Unsaturated alcohols, typically oleyl alcohol, are compounds which are useful in themselves or as alkylene oxide adducts in the production of cosmetics, textile oil and so on.
In the prior art, such unsaturated alcohols have been conventionally produced from wax obtained from sperm whales by saponification or sodium metal reduction. After a law prohibited the catching of sperm whales, a method was proposed for producing unsaturated alcohols by ester reduction of unsaturated fatty acids prepared from triglycerides of unsaturated fatty acids such as beef tallow, pork tallow or the like, and/or methyl esters thereof. This is the method that has been mainly carried out since then.
In view of the recent BSE(Bovine Spongiform Encephalopathy) problem, attention has been increasingly focused on unsaturated alcohols prepared from vegetable fats and oils. In recent years, especially there has been a great demand for unsaturated alcohols prepared from vegetable fats and oils for use as materials in cosmetics including skin lotions, skin creams, shampoos, hair rinses, hair treatments and the like which are applied to the human body or hair. Further, attention is being paid to vegetable unsaturated alcohols as raw materials for cosmetics since the public image of a product produced from vegetable raw materials is favorable.
Unsaturated alcohols are used especially because of their retention of liquidity. Because turbidity and cloudiness of a liquid exceedingly impair its commercial value, a cosmetic product would not be qualified as a liquid cosmetic if it becomes turbid or solids precipitate at about 10° C. in the room of a Japanese house in winter without an air conditioner.
If a liquid product has too high a cloud point, small quantities of components in the product are likely to become crystalline, and the product easily becomes cloudy or turbid during storage. For example, a liquid product is partly crystallized in a drum or the like, and crystals precipitate, resulting in a tendency to change part of the formulation. Consequently when a liquid product lacks a low cloud point for practical use, it may lead to serious problems.
Unsaturated alcohols for use as a material for cosmetics are required to be stable to light and to be unvaried in color in the long term.
Furthermore, when an unsaturated alcohol is used as an alkylene oxide adduct, it needs to be resistant to being colored in the presence of any potassium hydroxide used as a catalyst. Moreover, when an unsaturated alcohol is used to esterify a saturated or unsaturated fatty acid, lactic acid, phosphoric acid or the like, the ester is required to be resistant to being colored in the presence of any p-toluenesulfonic acid or sulfuric acid used as a catalyst. In addition, when an unsaturated alcohol is used in a sulfuric acid ester salt, the sulfuric acid ester salt is required to be resistant to being colored in the presence of any chlorosulfonic acid, acidic SO3 gas or acidic sulfuric acid ester before neutralization.
When liquid vegetable unsaturated alcohols are used as a raw material for a derivative in cosmetics, they must be stable to coloring in the presence of acidic or basic substances.
An unsaturated alcohol used as a material for cosmetics is required to give off little or no odor. Furthermore, cosmetic products containing such unsaturated alcohols must not vary in smell nor take a prolonged time to emit their smell.
For example, the following documents disclose liquid vegetable unsaturated alcohol products and processes for preparing them.
(1) Japanese Unexamined Patent Publication (PCT) No. 1997-504013 (page 6, lines 23 to 26; Examples 1 to 3, and elsewhere) discloses a vegetable unsaturated alcohol mixture having an iodine value of 20 to 110 and a process for preparing the same using a CuCrO4 catalyst. The publication describes that the obtained vegetable unsaturated alcohol mixture is an unsaturated aliphatic alcohol mixture that is stable to oxidation and exhibits a preferred low-temperature behavior. The document mentions that unsaturated aliphatic alcohol mixture containing 4.5% or less of conjugated dienes are excellent in terms of stability to oxidation. The document sets forth a working example wherein an unsaturated aliphatic alcohol mixture having an iodine value of 73.9, a conjugated diene content of 3.2%, and a softening point of 22.9° C. was prepared using a CuCrO4 catalyst.
The words “a preferred low-temperature behavior” used in the document shows that the softening point is low. Since the softening point is a temperature at which a solid partly starts to melt and becomes soft while it is heated, such low-temperature behavior is said to be due to the melting point of the main component in the solid.
(2) Japanese. Unexamined Patent Publication (PCT) No. 1998-502654 (page 9, line 24 to page 10, line 6; page 12, lines 8 to 9; Table 3, and elsewhere) discloses a vegetable unsaturated alcohol having an iodine value of 85 to 100 which is prepared from a laurin oil-derived unsaturated fatty acid, and a process for preparing the same by a fixed bed reactor of Cu/Cr/Zn or Cu/Cr/Cd mixed oxide-type or in a trickle phase of a silica gel-supported catalyst containing 20 to 40% by weight of copper chromite. The document also sets out that the obtained vegetable unsaturated alcohol is stable to oxidation and exhibits a preferred low-temperature behavior.
The term “preferred low-temperature behavior” used in the document denotes that the solidifying point is low. More specifically, the solidifying point is a temperature at which a liquid starts to solidify as a whole while the liquid is cooled. Thus, the document shows that such low-temperature behavior is due to the melting point of the main component in the liquid.
The solidifying point or softening point of unsaturated alcohols can be relatively easily controlled by selecting the type of main components. On the other hand, however, it is very difficult to control the production of small quantities of crystalline components which are responsible for the increase in the cloud point of unsaturated alcohols in the prior art process for preparing unsaturated alcohols, especially in those prior art processes using a hydrogenation catalyst. This problem has not yet been satisfactorily overcome.
Japanese Unexamined Patent Publications (PCT) No. 1997-504013 and No. 1998-502654 entirely lack disclosure color stability in the presence of an acidic or basic substance and long-term coloring resistance to light.
(3) Japanese Unexamined Patent Publication No. 2001-89403 (claim 1, paragraph 0040, Table 1 on page 5, and elsewhere) discloses a process for preparing an unsaturated alcohol by hydrogenation of an unsaturated fatty acid or an ester thereof using a zinc-chrome oxide catalyst or a zinc-chrome-aluminum oxide catalyst containing 100 ppm or less of copper and 200 ppm or less of nickel calculated on a metal basis. Further, the publication describes a working example in which an unsaturated alcohol mixture having an iodine value of about 92 and a cloud point of 0.5 to 2.1° C. was prepared by hydrogenation of an industrial unsaturated fatty acid using a zinc-type catalyst having a copper content of 15 to 20 ppm and a nickel content of 20 to 60 ppm.
Unsaturated fatty acids for industrial use are usually prepared from animal fats and oils as starting materials. Unsaturated fatty acids and unsaturated alcohols prepared from animal fats and oils as starting materials are generally unlikely to induce cloudiness at a low temperature. Although the reason for this phenomenon is unknown, it is presumable that fatty acids derived from animal fats and oils include fatty acids having an odd number of carbon atoms, and the finally obtained unsaturated alcohols comprise numerous components.
On the other hand, unsaturated fatty acids derived from vegetable fats and oils only have an even-number of carbon atoms. Consequently it is difficult to provide an unsaturated alcohol end-product which is unlikely to cause cloudiness at low temperatures.